Gas storage materials, including hydrogen storage materials

ABSTRACT

A material for the storage and release of gases comprises a plurality of hollow elements, each hollow element comprising a porous wall enclosing an interior cavity, the interior cavity including structures of a solid-state storage material. In particular examples, the storage material is a hydrogen storage material such as a solid state hydride. An improved method for forming such materials includes the solution diffusion of a storage material solution through a porous wall of a hollow element into an interior cavity.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

This invention was made under CRADA CR-04-003 between Toyota MotorEngineering & Manufacturing North America, Inc., and Savannah RiverNational Laboratory, operated for the United States Department of Energyby Savannah River Nuclear Solutions, LLC. The Government has certainrights in the invention.

FIELD OF THE INVENTION

The present invention relates to gas storage materials, such as hydrogenstorage materials.

BACKGROUND OF THE INVENTION

There are many possible applications of hydrogen fuel, such ashydrogen-powered vehicles. However, hydrogen in the gaseous state ishighly explosive. In the field of hydrogen-powered vehicles, hydrogenmay be stored on board the vehicle in high pressure tanks, for exampleat 5,000-10,000 psi gas pressure. Such storage systems are not efficienton a volumetric level, and also present serious safety concerns. Thereis a great commercial need for new methods of storing hydrogen in a safemanner.

SUMMARY OF THE INVENTION

Examples of the present invention provide improved solid state storageof gases, in particular storage of hydrogen using metal hydrides such asalanates or borohydrides. A storage material allows release andoptionally uptake of a gas, such as a hydride in the case of hydrogenstorage materials. The storage material may be disposed as nanoscalestructures within an interior cavity of a hollow element, for example onthe inside surfaces of the hollow elements. The hollow elements mayhollow glass elements, for example hollow glass microspheres. The hollowelements may have a porous wall surrounding an interior cavity, whichallow introduction of the storage material as a solution into theinterior, and removal of the solvent to leave structured solid forms ofthe storage material within the interior of the hollow element, such aselongated structures (such as needle-like nanocrystals) grown on aninterior surface of the porous wall, for example elongate crystalsnucleated onto surface defects of the interior surface.

Embodiments of the present invention include solid state hydrogenstorage materials encapsulated within porous-walled hollow elements suchas hollow glass microspheres. Hydrogen storage materials include complexmetal hydrides, including solid hydride materials such as alkaline andalkaline earth cation based alanates (alkali metal aluminum hydrides oralkaline earth metal aluminum hydrides) or borohydrides. Complex metalhydride materials are generally air and moisture sensitive, and may bedangerously reactive in bulk. Examples of the present invention includecomposite materials including such storage materials within the cavitiesof hollow elements, allowing safer handling of storage materials forapplications such as vehicles, including automobiles and the like.

In particular, examples of the present invention include methods andmaterials that facilitate the safer storage of reactive hydrogen storagematerials, such as reactive metal hydrides. Examples of the presentinvention allow reduced exposure of a storage material to air andmoisture, and allow easier handling of the storage materials, forexample within an onboard tank of a vehicle.

Examples of the present invention include a method of encapsulating agas storage material, such as a hydride, in a hollow element, the hollowelement having an interior cavity surrounded by a porous wall, bydissolving the storage material in a solvent and allowing the resultingstorage material solution to diffuse into the interior of the hollowelement. The storage material may be precipitated within the hollowelement by evaporating the solvent, for example under reduced pressuresuch as a partial vacuum. In representative examples, the hollow elementis a hollow glass microsphere (HGM).

An example material for the storage and release of a gas, such ashydrogen, comprises a plurality of hollow elements, each hollow elementcomprising a gas-permeable wall enclosing an interior cavity, theinterior cavity including a solid state gas storage material in the formof nanostructures. The hollow elements may be glass spheres havingporous walls enclosing the interior cavity, such as glass microsphereshaving an average diameter of between 1 micron and 500 microns, moreparticularly between approximately 5 microns and approximately 100microns. The porous walls may include pores having an average porediameter in the range of 10 Angstroms to 3000 Angstroms, and the averagewall thickness may be between 0.1 microns and 50 microns, moreparticularly between approximately 0.5 microns and approximately 5microns. The storage material may be a metal hydride such as an alkalimetal alanate, an alkaline earth metal alanate, an alkali metalborohydride, an alkaline earth metal borohydride, or a combinationthereof.

An example method of preparing a material for storage of gases comprisesproviding a hollow element having a porous wall enclosing an interiorcavity, introducing a storage material into the interior cavity bydiffusion of a solution of the storage material through the porous wall,the solution being the storage material dissolved in a solvent, andremoving the solvent from the interior cavity so as to precipitatenanostructures of the storage material within the interior cavity, forexample onto the interior surface of the porous wall.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a flow chart of preparing improved storage materials;

FIG. 2 is a schematic of an improved storage material;

FIG. 3 is an electron micrograph showing sodium alanate encapsulation ina porous glass sphere;

FIG. 4 is an electron micrograph of nanoscale sized alanate basedbundled structures on the inner surface of a porous glass sphere; and

FIGS. 5A-5E illustrate elemental distributions through a porous glasswall.

DETAILED DESCRIPTION OF THE INVENTION

Examples of the present invention facilitate safe storage of reactivehydrogen storage materials without greatly compromising the propertiesof the storage materials. In some examples, the storage materials areprovided as nanoscale structures within hollow elements, such as bundlesof needle-like nanocrystals having a cross-sectional dimension (width)of less than approximately 1 micron. The hollow elements reduce theeffects of ambient oxygen and moisture on the storage materials locatedtherein. The hollow elements may be porous wall hollow glass spheres,such as microspheres. The present invention is not limited to spheres,as the hollow elements may also comprise tubular structures, such aselongated hollow cylinders, ovoid forms, or other shapes. The hollowelements may be formed from any material stable in the intendedoperating environment such as silica-containing glass or other glasses,polymeric materials, ceramics, xeolites, and the like. Complex metalhydrides or other reactive materials may be encapsulated inside theporous walls of hollow elements.

Examples of the present invention include methods for encapsulating agas storage material in an interior cavity of a hollow glass element.The hollow glass element may be a hollow glass microsphere having: adiameter in the range of approximately 1 micron to approximately 200microns, more particularly a diameter of approximately 5 microns toapproximately 100 microns; and a wall thickness in the range ofapproximately 0.1 microns to approximately 50 microns, more particularlybetween approximately 0.5 microns to approximately 5 microns. An examplemethod includes chemical treatment (such as acid treatment) of the wallsof the hollow glass elements to form porous network structure therein.Hollow element parameters such as wall thickness, element diameter, andpore diameter may be average thickness and average diameters, forexample the median values for a representative sample of the hollowelements.

In some examples, a storage material is dissolved in a solvent toprovide a storage material solution. The solvent may be an organicsolvent such as tetrahydrofuran an ether (such as diethyl ether ordibutyl ether), a glyme (such as monoglyme, diglyme, or triglyme), orother solvent. In the case of alanates, preferred solvents includetetrahydrofuran or an ether such as diethyl ether. Heat and/or pressuremay be used to facilitate the dissolution of the storage material in thesolvent. The storage material solution is allowed to diffuse through thewalls of the hollow elements so that the storage material solutionenters the interior of the hollow elements. The storage materialsolution can be introduced in a low pressure environment (such as apartial vacuum) to facilitate solution entry into the cavities of thehollow elements. The storage material precipitates within the cavitiesof the hollow elements as the solvent evaporates.

Further, after solvent removal from the interior, a hydrogen-selectivemembrane such as a silica-based inorganic membrane, may be disposed onthe outer surface of the glass elements using any appropriate method,such as a dry vacuum deposition process or wet sol-gel process.

The hollow elements may be hollow glass microspheres, such as hollowglass microspheres comprising a silica-based glass. In representativeexamples, the hollow elements are hollow glass spheres having a diameterin the range of approximately 5 microns to approximately 100 microns,and wall thickness or approximately 0.5 microns to approximately 5microns. The hollow microspheres need not be perfectly spherical, sothat the term diameter may represent any cross-sectional distancethrough an approximate center, and the wall thickness may be a meanvalue wall thickness for a variable thickness wall. The hollow glassspheres may initially have a non-porous wall, with pores introducedthrough a pore formation process. For example, hollow glass spheres maybe treated with mineral acid to allow for porous network structureformation.

Examples of the present invention include a composite material in whichreactive solid storage materials are encapsulated within the cavities ofhollow elements, such as hollow glass spheres.

FIG. 1 shows a flow chart of an exemplary method. Box 10 corresponds toproviding hollow elements with porous walls, each having at least oneinterior cavity surrounded by a wall that is at least in part porous.Box 12 corresponds to providing a storage material solution. Box 14corresponds to introducing the storage material solution into thecavities of the hollow elements. Box 16 corresponds to removing thesolvent from the cavities. After solvent removal, storage material islocated within the cavities of the hollow elements.

FIG. 2 is a simplified cross-sectional schematic of an improved gasstorage material according to embodiments of the present inventiongenerally at 20. The figure shows a hollow element having a wall 20enclosing an interior cavity 28. Pores, such as pore 24, allow fluids(liquids or gases) to pass from outside the hollow element into theinterior cavity and vice versa. The figure shows a few representativepores, though preferably there are many more than shown. Hence, the wallis porous, but the pore distribution need not be uniform. The storagematerial is disposed as structures 26 on the interior surface 34 of thehollow element, and may also be present as particles 30 within theinterior cavity 28. The structures may include elongated structures,such as needle-like crystals and bundles thereof, supported on theinterior surface. An optional gas permeable membrane 32 (shown in partonly) may be disposed on the exterior surface 36. The storage materialmay block some fraction of the pores.

EXAMPLES

Example composite materials were prepared. Hollow glass spheres wereacid leached to allow for a porous network structure formation. Theencapsulation procedure included dissolution of a reactive solid storagematerial in a solvent such as tetrahydrofuran (THF) or an ether such asdiethyl ether. The dissolution was carried out at room temperature andambient pressure, but elevated temperature and/or pressure may be usedto enhance the dissolution of the material in the solvent. The solutionwas allowed to diffuse to occur through the pores of the hollow glassspheres walls. Precipitation of the reactive storage material within theinterior cavity of the hollow spheres resulted from evaporating thesolvent under vacuum.

Hollow spheres were prepared using phase-separated glass, as discussedin more detail below, and the microspheres were had porous walls withmost pore diameters in the range of 100 Angstroms to a few thousands ofAngstroms (e.g. 3,000 Angstroms). In other examples, pore diameters mayrange from approximately 10 Angstroms to approximately 1000 Angstroms.Sodium alanate diffusion at room temperature into the interior cavity ofthe glass spheres was allowed through solution diffusion, using NaAlH₄dissolved in a tetrahydrofuran solvent. Microscopy characterizationconfirmed the encapsulation of the sodium alanate in the interior cavityof the hollow glass microspheres. Characterization followed passivationof the encapsulated alanate in air.

The presence of nanoscale-size crystal formation was observed on theinterior surface of the glass wall. This shows that nano-crystalliteformation of sodium alanate can be achieved by precipitating alanate ona silica surface. In this context, a nanocrystallite is a crystallitehaving a dimension (such as measured along a dimension normal to thedirection of elongation) of less than a few microns, in some examplesless than approximately 1 micron.

FIG. 3 shows a scanning electron micrograph (SEM) showing proof ofsodium alanate encapsulation within the wall of a porous glass sphere.The alanate diffused through the pores of the glass wall by solutiondiffusion into the interior cavity. Solvent removal from the interiorcavity caused precipitation of the sodium alanate, and the sodiumalanate was exposed to air prior to this SEM imaging. The alanate existsas needle-like structures within the interior cavity, facilitatinghydrogen exchange.

This SEM micrograph demonstrates alanate precipitation and encapsulationfollowing diffusion through the walls of porous glass spheres. Thealanate material within the hollow spheres diffused through the pores ofthe glass walls by solution diffusion, followed by precipitation, andwas exposed to air prior to the SEM imaging.

FIG. 4 shows a SEM micrograph of nanoscale sized sodium alanate bundledstructures formed on the inner surface of a porous glass spherefollowing sodium alanate precipitation and exposure to air. The interiorsurfaces of the silica-containing glass spheres provided nucleationsites for nano-sized sodium alanate crystal growth.

These figures demonstrate, for the first time, a nanostructured hydrogenstorage material having a much greater surface area than the surfacearea of the interior surface facing the interior cavity. Thisfacilitates release (and uptake) of a stored gas. Embodiments of thepresent invention include hollow elements including an interior cavity,the interior cavity being bounded by a porous wall having an interiorsurface area facing the cavity and including a structured solid stategas storage material presenting a surface area at least one order ofmagnitude greater than the interior surface area, and in some examplesat least three orders of magnitude greater.

Materials allowing the storage and release of a gas may comprise aplurality of hollow elements each having a porous wall disposed aroundan interior cavity, the wall having an interior surface facing theinterior cavity and an exterior surface, the interior cavity including asolid state gas storage material including structures supported by theinterior surface of the wall, such as crystals nucleated by the interiorsurface of the wall. The structures may include microcrystals and/ornanocrystals, and may include elongated crystals such as needle-shapedcrystals. An elongate form may have a length to width (e.g.cross-sectional diameter) ratio of at least approximately 3:1, and insome cases at least approximately 10:1. The elongated crystals may havea length, such as a median length, between 0.1 microns and the interiordiameter of the interior cavity, such as between 0.1 microns and 10microns, and a cross-sectional dimension (e.g. width) of less than 1micron, more particularly between 0.1 microns and 1 micron.

FIGS. 5A-5E illustrate elemental mapping for a cross-section of part ofthe wall of a porous silica glass sphere. FIG. 5A shows an electronmicrograph, with the wall occupying most of the image, and an edge ofthe porous wall at the upper right of the image. These images are notnecessary for an understanding of the present invention, but illustratethe presence of sodium and aluminum through the porous wall, indicatingdiffusion through the pores has occurred. FIGS. 5B, 5C, 5D, and 5E showaluminum, silicon, oxygen, and sodium distributions respectively, withdark regions indicating higher concentrations of the relevant element.The distribution of the sodium alanate elements (Na and Al) across thewall confirms through wall diffusion.

The presence of sodium and aluminum across the wall of a porous sphereillustrates alanate diffusion through pores. Elemental mapping of aporous glass sphere cross-section, discussed above, showed thedistribution of sodium alanate elements (Na and Al) across the wallwhich confirmed through-wall diffusion in the encapsulation process. Thenovel encapsulation process further allows new alanate compositions tobe created, and nanostructures to form.

The encapsulated form of alanate, in the form of solid state alanatewithin interior cavities of the hollow elements, can greatly reduce thewell-known sodium alanate reversibility problem, following alanatedehydrogenation to aluminum metal and sodium hydrides. The reversibilityproblem is believed to be due to long-range diffusion between thealuminum and the sodium hydride formed following decomposition of thesodium alanate, and the use of alanate nanostructures reduces thealuminum metal diffusion path and may greatly improve reversibility. Insome examples of the present invention, alanate reversal is possiblewithout the use of dopants such as titanium, which are conventionallyrequired with alanate storage materials.

A hydrogen selective permeable membrane such as silica based inorganicmembrane can be disposed on the outer surface of the hollow spheres ifdesired, for example using a dry vacuum vapor deposition process or awet sol get process.

Storage Materials

Hydrogen storage materials include hydrides, such as complex metalhydrides, including alanates and borohydrides. Examples include alkaliand alkaline earth cation based alanates or borohydrides. Hydrogenstorage materials also include metals forming interstitial hydrides,palladium. Alkali cation alanates include sodium alanate (sometimesreferred to as sodium aluminum hydride). The formula of sodium alanateis sometimes written as NaAlH_(z), where z is 4, but the term sodiumalanate includes non-stoichiometric forms in which the ratio of sodiumand aluminum may vary from unity, and further the parameter z may alsovary depending on the circumstances, environment, and application.

Specific examples of storage materials include metal hydrides such assodium alanate (sodium aluminum hydride), lithium alanate (lithiumaluminum hydride), transition metal alanates such as titanium alanate(titanium aluminum hydride), other complex hydrides, borohydrides (suchas lithium borohydride, also including catalyzed borohydrides), andcombinations of two or more hydrogen storage materials. A metal hydridemay be chosen to be solid at room temperature, or solid over a typicaloperational range of an apparatus using the storage material as a sourceof hydrogen fuel.

Example complex metal hydrides may have a formula of the formM_(a)M′_(b)H_(z), where M is a metal cation or cation complex, and M′ isa metal or metalloid. For example, M may be an alkali metal cation,alkaline earth metal, other metal, or metal complex, and M′ may be agroup 13 element such as boron or aluminum. Complex metal hydrides alsoinclude salts such as [MgBr(THF)₂]₄FeH₆ and K₂ReH₉.

Storage materials also include palladium, and transition metals or othermetals capable of forming storing interstitial gas.

However, the present invention is not limited to the storage of hydrogengas. Storage materials may be used to store other gases, such asmethane, other hydrocarbons, other fuels, halogens, or other gases, inparticular gases that react with oxygen and/or water Particularembodiments of the present invention include methane storage within theinterior cavity of a porous wall hollow glass microsphere.

Hollow Elements

Hollow elements may be in the form of hollow microspheres, tubes (suchas cylinders), or other forms. Preferably, the hollow elements haveporous walls to facilitate introduction of the storage material into oneor more interior cavities by solution diffusion.

The hollow elements may be formed from any material that issubstantially stable in the intended operating environment. Examplehollow element materials include silica-containing glasses (includingsilica glass, silicate glasses, and the like), other glasses, polymericmaterials, ceramics, xeolites, inert metals, and the like.

The material used to form the hollow elements may include othercomponents or have other physical properties. For example, a coloringagent may be used to help identify the resulting composite storagematerial, an optical absorber used to prevent radiation from inducingdecomposition of a material if the material is exposed to light,chemical stabilizers, catalysts to promote gas release, or otherpurpose.

Porous walls may be formed by acid etching of a material including anextractable component. In other examples, porous walls may be formed byany appropriate etching process, depending on the material used to formthe hollow element.

The porous wall of a hollow element may have the form of a sphericalshell. However, the wall need not be exactly spherical, and may begenerally spheroidal. In other examples, the wall may be a prolatespheroidal shell, an elongate cylinder with capped or open ends, orother form.

The interior cavity may be a generally open space. However, in otherexamples, an interior cavity may include a lattice structure, particles,or other intrusions. There may be a plurality of interior cavities in asingle hollow element.

Hollow Microsphere Formation

As described in US Published Application 2006/006820 to Schumacher etal., and also WO/2007/050362 to Wicks et al., hollow glass microspheresmay be prepared using a glass composition that separates into twocontinuous glass phases after appropriate heat treatment. For example,one of the phases may be rich in silica, the other being an extractablephase such as a boron-containing material, for example borosilicates oralkali-metal borosilicates. Suitable borosilicates and alkali-metalsilicates include the leachable glass fiber compositions disclosed inU.S. Pat. No. 4,842,620.

The glass components are mixed, melted, quenched, and crushed to a fineglass powder having a particle size of about 5 to 50 microns. The glassparticles reheated to a temperature where a latent blowing agent causesa bubble to nucleate within each glass particle, and as the temperatureincreases, the pressure within the bubble exceeds the surfacetension/viscous forces so that the bubble expands to form a hollow glassmicrosphere.

Using such an approach, as described in US Published Application2006/0060820 to Schumacher et al., the resulting hollow glassmicrospheres have densities in the range of about 0.05 gm/cc to about0.5 gm/cc, and diameters may range between about 1 to about 140 microns.Hollow glass microspheres may be separated on the basis of density so asto select microspheres according to a desired density range.Microspheres may also be separated according to their diameter.

The hollow glass microspheres may be heat treated to enhance theglass-in-glass phase separation. The extractable phase is readilyleachable using strong mineral acids which results in the formation ofwall pores within the remaining silica-rich phase. Suitable mineralacids and methods for leaching the glass are described in U.S. Pat. No.4,842,620.

The resulting hollow glass microspheres have a high degree of cell wallporosity, in the form of a plurality of pores and similar openings whicheither directly or indirectly allow fluid communication between theinterior and the exterior of the microspheres. An average cell wall porediameter of about 10 Angstroms to about 1000 Angstroms can be achievedusing this approach. The cell wall porosity is dependent upon thepercentage of extractable components within the original glasscomposition, and the heat treatment employed. The extraction process caninfluence the size and density of pores formed. Such hollow glassmicrospheres with porous walls are well suited for use with examples ofthe present invention.

Encapsulation and Formation of Hydrogen Storage Composites

Storage materials can be introduced into the interior of porous-wallhollow elements using solution diffusion through the porous wall intothe interior. The interior may optionally be vacated of air or othergases using a vacuum pump, the hollow elements dispersed through astorage material solution, and atmospheric or elevated pressure used toinduce solution diffusion through the porous walls and into the interiorof the hollow elements. Solvent may be removed using heat and/or reducedpressure, including vacuum drying. A number of solution diffusion stepsmay be used to increase storage material intake into the hollowelements.

Hydrogen, possibly in the form of high pressure gas introduced throughthe porous walls, may be used to further hydrogenate or otherwise reducethe storage material if desired. After encapsulation, hollow elementsmay be coated with a hydrogen-permeable membrane, for example byapplying a coating material such as tetraethyl orthosilicate (TEOS)solution, or other silane or ormosil, to form a sol-gel layer. Thehydrogen-permeable membrane can be chosen to permit the diffusion ofhydrogen through the membrane, while excluding other gases. In otherexamples, the pore diameter may be initially formed to permit hydrogendiffusion through the pores while excluding other gases.

Hence, a material for the storage and release of hydrogen comprises aplurality of hollow glass microspheres, each microsphere a having porouswall enclosing an interior cavity including a gas storage material inthe form of nanostructures of a solid metal hydride. The hollow glassmicrospheres may have a diameter of between 1 micron and 500 microns,and example solid metal hydrides include an alkali metal alanate, analkaline earth metal alanate, an alkali metal borohydride, an alkalineearth metal borohydrides, or some combination of hydrides, such as amixture of alanate(s) and borohydride(s).

The hollow elements undergo a surface treatment, for example beingtreated with a surfactant, so as to make at least the outer wallhydrophobic, so as to repel moisture. This may occur before or afterintroduction of a storage material.

Hydrogen Storage and Release

After encapsulation in the hollow elements, the storage material may besubjected to variations in temperature, pressure, or other stimulus soas to release hydrogen gas. A de-hydrided storage material may then beused to selectively absorb hydrogen gas. Release and absorption of thehydrogen is possible through the porous walls of the hollow elements.

Some examples of the present invention relate to providing improvedmaterials that facilitate the safer storage and release of a gas such ashydrogen, the material comprising a plurality of hollow elements havinga porous wall (the wall including a plurality of pores, which need notbe uniformly distributed) enclosing an interior cavity, the wall havingan interior surface facing the interior cavity and an exterior surface,the interior cavity including a gas storage material, preferably solidstate and including structures supported by the interior surface of thewall. The structures may include microcrystals and/or nanocrystals, andmay include elongated crystals such as needle-shaped crystals. Theelongated crystals may have a length, such as a median length, between0.1 microns and 50 microns, more particularly between 0.1 microns and 10microns, and a cross-sectional dimension (width) of less than 1 micron,more particularly between 0.1 microns and 1 micron.

The invention is not restricted to the illustrative examples describedabove. Example methods, materials, applications, and compounds describedare exemplary, and are not intended to limit the scope of the invention.Changes therein, other combinations of elements, and other uses willoccur to those skilled in the art. The scope of the invention is definedby the scope of the claims.

1. A material allowing the storage and release of a gas, the materialcomprising: a plurality of hollow elements, each hollow element having aporous wall surrounding an interior cavity, the porous wall having aninterior surface facing the interior cavity, the interior cavityincluding a gas storage material in the form of elongate structuressupported by the interior surface of the porous wall, the elongatestructures being needle crystals grown from the interior surface of theporous wall, the elongate structures having a length to width ratio ofat least approximately three to one, the hollow elements being hollowglass elements, the gas being hydrogen, the gas storage material beingan alkali metal alanate or an alkaline earth metal alanate.
 2. Thematerial of claim 1, the elongate structures having a length between 0.1microns and 10 microns, and a cross-sectional dimension of less than 1micron.
 3. The material of claim 1, the elongate structures having alength of between 0.1 microns and 50 microns, and a cross-sectionaldimension of between 0.1 microns and 1 microns.
 4. The material of claim1, wherein the storage material is sodium alanate.
 5. The material ofclaim 1, wherein the hollow elements are glass spheres.
 6. The materialof claim 5, wherein the glass spheres are glass microspheres having anaverage diameter of between 1 micron and 500 microns.
 7. The material ofclaim 5, wherein the glass spheres are glass microspheres having anaverage diameter of between approximately 5 microns and approximately100 microns.
 8. The material of claim 5, wherein the porous wallincludes pores having an average pore diameter in the range of 10Angstroms to 3000 Angstroms.
 9. The material of claim 5, wherein theporous wall has an average wall thickness of between 0.1 microns and 50microns.
 10. The material of claim 5, wherein the porous wall has a wallthickness of between approximately 0.5 microns to approximately 5microns.
 11. A material for the storage and release of hydrogen, thematerial comprising: a plurality of hollow glass microspheres, eachhollow glass microsphere comprising a porous wall enclosing an interiorcavity, the porous wall having an interior surface facing the interiorcavity having an interior surface area, the hollow glass microsphereshaving an average diameter of between 1 micron and 500 microns; and agas storage material disposed within the interior cavity, the gasstorage material including elongate structures of a solid metal hydridesupported by the interior surface of the porous wall, the gas storagematerial within the interior cavity presenting a surface area at leastone order of magnitude greater than the interior surface area, theelongate structures being needle crystals grown from the interiorsurface of the porous wall, the gas storage material being an alkalimetal alanate or an alkaline earth metal alanate.
 12. The material ofclaim 11, wherein the solid metal hydride is sodium alanate.